River flow and associated transport of sediments and solutes through a highly urbanised catchment, Bradford, West Yorkshire.

The hydrological characteristics of catchments become drastically modified in response to urbanisation. The total contributions and dynamics of runoff, suspended sediment and solutes may change significantly and have important implications downstream where they may affect flooding, instream ecological habitat, water quality and siltation of river channels and lakes. Although an appreciation of the likely hydrological changes is crucial for effective catchment management they are still poorly understood. In this paper we present data from a network of river monitoring stations throughout the heavily urbanised Bradford catchment, West Yorkshire. Sites are upstream, within and downstream of the highly urbanised central part of the catchment. Flow, turbidity (calibrated to suspended sediment concentration) and specific conductance (surrogate for solute concentration), logged at 15-min intervals, are presented for a 12-month period (June 2000 to June 2001). The total amounts and dynamics of flow, solute and suspended sediment transport were investigated. Estimated total flow and suspended sediment transport for the monitoring period were found to be high in response to the high total rainfall. Flow and sediment transport regimes were extremely 'flashy' throughout the catchment and became increasingly flashy in a downstream direction. Suspended sediment discharged from the Bradford subcatchment makes an important contribution to downstream sediment transport on the river Aire at Beal. Data suggest that the urbanised part of the Bradford catchment is extremely important in contributing solutes to the Beck (river). Although flow and sediment are also contributed to the Bradford Beck in the urbanised part of the catchment the data suggest that significant amounts may enter the combined sewer system and bypass the river. Understanding the spatial and temporal variations of flow and the transport of suspended sediment and solutes in rivers in urbanized subcatchments is crucial to their effective management and monitoring. Furthermore, this knowledge may be extremely important to the management and monitoring of downstream rivers in large scale mixed catchments.

The impact of a convectional summer rainfall event on river flow and fine sediment transport in a highly urbanised catchment: Bradford, West Yorkshire.

Urban watercourses are important assets to cities, but they often have extremely 'flashy' hydraulic regimes and poor water quality, making them potential hazards. Current knowledge of the impact of intense rainfall events on urban river water discharge and, in particular, fine sediment transport is limited. Continuous monitoring of flow and turbidity (subsequently calibrated to suspended sediment concentration) was undertaken at a network of four sites throughout the highly urbanised Bradford catchment in West Yorkshire, NE England. An intense convectional rainfall event, which occurred over central Bradford in June 2001, generated extreme flow and fine sediment transport responses at the most downstream site, Shipley Weir. In just 15 min, discharge increased from 0.45 to 34.6 m(3) s(-1) (median annual peak instantaneous discharge of 27.5 m(3) s(-1), 1983-2001) and suspended sediment concentration increased from 14 to 1,360 mg l(-1). A peak sediment flux of 47.2 kg s(-1) was recorded. It is demonstrated that this extremely large and urban flux of fine sediment is likely to have a major downstream impact on water quality in the River Aire.